This invention relates to a power transmission chain belt and, in particular, to a power transmission chain belt for use with a continuously variable transmission (CVT). The belt is comprised of a large number of interleaved link plates which are placed parallel to the chain rotational direction and carry a number of load blocks or struts for transmission of power to the variable width pulleys of the CVT. The belt is formed of a plurality of adjacent chain portions that are offset or phased by a portion of one chain pitch. Preferably, the belt is formed of at least three adjacent chain portions that are offset or phased by one-half pitch.
An example of a power transmission chain belt for a CVT is shown in FIG. 15 of the drawings. As shown in that figure, the CVT includes input shaft 101a and output shaft 102a, which carry primary (drive) and secondary (driven) pulleys 103a, 104a, respectively. The chain belt 105a interconnects the primary and secondary pulleys of the CVT.
Primary pulley 103a includes fixed pulley portion 103a', which is fixed to input shaft 101a, and moveable pulley 103b', which is moveable along input shaft 101a. Similarly, secondary pulley 104a includes fixed pulley 104a', which is fixed to the output shaft 102a and moveable pulley 104b', which is moveable along the output shaft. The effective diameters of pulleys 103a and 104a are changed by movement of the moveable pulley portions 103b', 104b', which is caused by operation of hydraulic actuators, as is known in the art. In this manner the speed change ratio between the input and output shafts can be varied continuously.
An example of a two-way phased chain belt of the prior art is shown in FIG. 16 and includes two chains or chain portions 110a, 111a. The chain also includes load blocks or struts 112a, which are arranged in the direction of the length of the chain and extend across the width of the chain. The chains 110a, 111a are connected alternately by the struts passing between both chain widths. The pulleys contact the outside edges of the struts to pass power between the chain and the pulleys.
The chains are each comprised of link plates that are connected by connecting pins 106a, 107a. Protrusion 118a is formed at the connection of the chain to each strut to prevent displacement of the strut in the chain width direction (the left to right direction in FIG. 16).
Examples of phased transmission chains for CVTs are shown in U.S. Pat. Nos. 5,645,502 and 5,453,058, which are incorporated herein by reference. When these transmission chains are used, noise is generated as the load blocks or struts contact the sides of the pulleys. Efforts have been directed to decreasing the noise generated during such contact while maintaining a durable chain. Efforts at decreasing noise generation have involved, for example, using links of more than one pitch length, alternating the lengths of the struts, and changing the length of the windows of the links that receive the struts.
Other efforts at noise reduction in the prior art have included the use of two chain portions positioned in side-by-side relationship, but offset or phased by one-half pitch length. Other phased chains of the prior art have utilized three chain portions positioned in side-by-side relationship, but with the center portion offset from the two outside chain portions by a distance of one-half pitch length. The chain of the present invention is directed to this type of phased chain with three chain portions.